Intracellular and extracellular concentrations of various ionic species have important consequences on neuronal excitability. There is good evidence to suggest that glia play an important role in regulating both intracellular and extracellular ionic concentrations and thus regulatte neuronal excitability. It will be the purpose of this investigation to quantitate and compare: (1) the intracellular content of sodium, potassium, chloride and other ionic species in astrocytes from control and seizure-susceptible mice, (2) the ability of astrocytes from control and seizure- susceptible mice to accumulate potassium following exposure to varying concentrations of extracellular potassium and (3) the intracellular ionic content and the accumulation of potassium in astrocytes following an experimentally-induced seizure in seizure- susceptible mice and control mice which have been exposed to the same seizure-provoking stimulus. In measuring and quantitating intracellular elemental content, we will use electron probe x-ray microanalysis of neocortex of astrocytes, grown in tissue culture, from control (C57) and seizure-susceptible mice (DBA/2J). This technique permits an accurate quantification of elemental content at both the cellular and subcellular level. We anticipate that adnormal concentrations of sodium, potassium or chloride may be present in the astrocytes from seizure- susceptible mice and/or the ability of such astrocytes to regulate extracellular potassium concentrations may be diminished as compared to that of astrocytes from control mouse brain. The finding of this study have implications with regard to the neurophysiological mechanisms involved in the generation of seizure disorders and, ultimately, to the development of more effective anticonvulsant drugs.